28 PROF. W. C. WILLIAMSON ON THE 



III. On the Organization of Volkmannia Dawsoni, an un- 

 described Verticillate Strobilus from the Lower Coal- 

 measures of Lancashire. By W. C. Williamson, 

 F.R.S., Professor of Natural History in Owens Col- 

 lege, Manchester. 



Eead February 7th, 1871. 



In his " Observations on the Structure of Fossil Plants 

 found in the Carboniferous Strata/' Mr. Binney has figured 

 three types of verticillate spikes of cryptogamic fructifi- 

 cation, which in all probability represent three very dif- 

 ferent groups of plants. In plates 4 and 5 he has given 

 the structure of one of these types under the name of 

 Calamodendron commune. The same type has received 

 from Mr. Carruthers the name of Volkmannia Binnei 

 (Journal of Botany, Dec. 1867), whilst Prof. Schimper 

 has designated it Calamostachys Binney ana. At the last 

 Meeting of the British Association at Liverpool, I ad- 

 vanced my reasons for believing that this spike had no 

 relationship with the group of Calamites ; and the same 

 view is advanced in a still more recent " Memoir on tiie 

 Organization of Calamites," presented to the Royal Society. 

 In the type referred to, as is well known, the several nodes of 

 the central axis give off bractigerous disks and sporangio- 

 phores in alternate verticils. In his plate vi., Mr. Binney 

 figures a spike (fig. 1), in which the sporangia are very 

 compactly clustered in verticils, which are very closely 

 embraced by a bractigerous disk springing from each 

 node. I believe this figure represents the same plant as 

 that of which I recently described the internal organiza- 

 tion (" On a new form of Calamitean Strobilus from the 

 Lancashire Coal-measures/' Memoirs of the Literarv and 



